Integrated resource planners require consistent, credible, up-to-date information on the performance and cost of electricity generation technologies to develop viable long-term resource plans and technology strategies. EPRI’s Technology Assessment Guide (TAG) cost and performance basis provides a guideline in developing consistent technology cost and performance estimates for conventional and emerging power generation, energy system, and energy storage technologies. This report describes the TAG methodology used to develop technology cost and performance data and provides essential information to perform technical and economic evaluations of power generation and energy storage technologies as well as low-carbon energy supply technologies.